Conventionally, porous particles have been developed. JP-B 2550262 discloses an oil absorber containing an organic acid metal salt and an oil-absorbing crosslinked polymer, containing porous particles which swell by absorbing a large amount of oil, are excellent in an ability to retain absorbed oil, and significantly improve the rate of absorption of oil.
As a process for producing non-swelling porous particles, JP-A (W) 2000-516973 discloses porous spherical particles obtained by melt-mixing polypropylene with dichlorobenzole or amyl acetate for dissolving the polymer, then spray-cooling the mixture, and removing the solvent in a later step.